Objectives Study efficacy and mode of action for synthetic steroid HL9001 in SIV infected rhesus ABSTRACT:Synthetic corticosteroids have been proposed as immunotherapies in AIDS. We used the synthetic steroid HL-9001 to treat SIV infected rhesus. The drug had no visible side effects and was well tolerated by oral dosing when mixed with food treats. Treatement was initiated when animals showed low CD4 counts or sever wasting. In three cases, chronic administration of HL-9001 reconstituted CD4+ T cells, CD8+ T cells, and total leukocyte counts back to or above the levels present prior to infection. In two cases, sever wasting was reversed by drug administration although animals with wasting expired from hematologic failure, the HL-9001 appeared effective for treating this condition. These preliminary studies support further exploration of HL-9001 as an AIDS therapy. Keywords AIDS, therapy; steroid; wasting; CD4 cells